Multi-ply absorbent paper product having impressed pattern

ABSTRACT

A multi-ply tissue includes a first cellulosic embossed ply having an emboss pattern applied over a portion of its surface and a second cellulosic embossed ply of tissue. The first ply is contact laminated to the second ply so that the primary adhesion between the plies of tissue is the result of contact between cellulosic fibers. The first and second plies contact one another in contact areas, with the contact areas between the first and second plies defining compliant voids. The contact areas between the first ply and the second ply are elongated and/or rounded contact areas. A method of forming a multi-ply tissue involves conveying a base sheet through a nip between an impression roll and a pattern roll to produce an embossed base sheet having a back side possessing projections, applying adhesive to the back side of the embossed base sheet at spaced apart locations, and applying a flat backing sheet to the back side of the embossed base sheet so that the backing sheet adheres to the back side of the embossed base sheet at said spaced apart locations. A method of producing an embossed tissue involves successively conveying a base sheet through a nip between a first impression roll and a pattern roll, and conveying the base sheet through another nip between the pattern roll and a second impression roll, wherein the second impression roll is made of rubber having a lower hardness than the rubber from which the first impression roll is made.

This application is a continuation of application Ser. No. 09/564,800,filed May 5, 2000, which claims priority to and the benefits under 35U.S.C. §119(e) of Application Ser. No. 60/162,981, filed Nov. 1, 1999,and this application is a continuation of application Ser. No.11/465,837, filed Aug. 21, 2006, which is a divisional of applicationSer. No. 11/002,651, filed Dec. 3, 2004, which is a divisional ofapplication Ser. No. 09/564,800, filed May 5, 2000, which claimspriority to and the benefits under 35 U.S.C. §119(e) of Application Ser.No. 60/162,981, filed Nov. 1, 1999, of all of which are incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

This invention generally relates to absorbent paper products, includingtissue paper, towels, wipes and napkins. More particularly, the presentinvention pertains to an embossed multi-ply absorbent paper product.

BACKGROUND OF THE INVENTION

Consumer acceptance of absorbent paper products such as tissue paperproducts and the like is influenced by the perceived softness of thetissue product. Indeed, the consumer's perception of the desirability ofone tissue product over another is based in significant respects on theperceived relative softness of the tissue products; the tissue productthat is perceived to be more soft is typically perceived to be moreacceptable.

Thus, tissue paper should ideally possess a relatively high embossdefinition and bulk, and a relatively high degree of perceived puffinessand softness. The emboss definition and bulk of the tissue paper iscommonly found to affect the perceived softness of the tissue paper. Inaddition, the tissue paper should possess sufficient strength. However,it is typically the case that improving one or more of these parametersof the tissue paper adversely affects one or more of the otherparameters. For example, applying a very heavy embossing to the tissueproduct increases the embossing definition and bulk of the tissue paper,but also increases the friction so that the perceived softness isreduced. Also, a reduction in the strength of the tissue productresults. On the other hand, a less heavily embossed tissue product mightpossess better strength characteristics and smoothness attributes, butthe perceived puffiness and softness of the tissue product would beadversely affected.

Conventional deep embossing of two-ply tissue paper involves conveyingtwo plies of tissue paper through a nip formed between a steel roll anda rubber roll. While this type of embossing is able to provide betteremboss definition and puffiness, it also increases the back sidefriction which thus reduces tissue softness. Also, the rather heavyembossing adversely affects the strength of the resulting multi-plytissue.

U.S. Pat. No. 3,708,366 describes a method of producing two-ply papertowel in which one ply is more severely embossed than the other ply.This patent is not specifically related to the manufacture of tissuepaper products. Moreover, the patent describes that the preferredembossments are in the shape of a frustum of a cone. This embossmentshape produces non-elongated and rather sharply defined contact regionsbetween the two plies which have been found to result in a paper towelproduct having a rather harsh feel. While this resulting feel of theproduct may be acceptable from the standpoint of paper towel productssuch as that with which the aforementioned patent is concerned, it is aresult that is not well suited for tissue paper products.

There thus exists a need for a tissue product having better perceivedsoftness and bulk along with better emboss definition, without undulydegrading the strength characteristics of the tissue product.

A need also exists for a tissue that is heavily embossed, but which doesnot have the roughened characteristics typically associated with suchheavily embossed tissue. When multiple sheets are embossed together, thenubs or protuberances on the back side of the tissue are perceived asbeing rough by the consumer.

A need also exists for a one ply embossed sheet that does not possess atwo-sided look or appearance. One ply embossed sheets are typicallyembossed with matched steel-to-steel rolls and this produces theundesirable two sided look or appearance. Aside from this, the use ofsteel-to-steel emboss rolls to produce the one ply embossed tissuecreates undesirable paper dust and has a tendency to damage the steelemboss rolls.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a multi-ply tissue includes afirst cellulosic embossed ply having an emboss pattern applied over fromthree to twelve percent of its surface to a depth of at least aboutthirty thousandths of an inch, and a second cellulosic embossed ply oftissue in which the depth of emboss applied to the second ply is no morethan about 80% of the depth of emboss applied to the first ply. Thefirst ply is contact laminated to the second ply, with the primaryadhesion between the plies of tissue being the result of contact betweencellulosic fibers rather than through an intermediate adhesive. Thefirst and second plies contact one another in contact areas, with thecontact areas between the first and second plies defining compliantvoids and with the total contact area being no more than about fifteenpercent of the area of the tissue sheets.

According to another aspect of the invention, a method of producing atwo ply tissue involves embossing a first ply of tissue so that thefirst ply of tissue possesses an emboss pattern and embossing a secondply of tissue so that the second ply of tissue possesses an embosspattern, with the first ply being more heavily embossed than the secondply. The first and second plies are nested together to contact laminatethe first ply to the second ply with contact areas between the first andsecond plies, the contact areas being elongated or gently rounded.

In accordance with another aspect of the invention, a method ofproducing a two ply tissue involves conveying a base sheet through a nipbetween an impression roll sometimes made of rubber and a pattern rollsometimes made of steel to emboss a pattern on the base sheet andproduce an embossed base sheet having a back side possessing projectionsproduced by the pattern roll, applying adhesive to the back side of theembossed base sheet at spaced apart locations so that portions of theback side of the embossed base sheet between the projections are devoidof adhesive, and applying a flat backing sheet that is devoid ofembossing to the back side of the embossed base sheet to cause thebacking sheet to adhere to the back side of the embossed base sheet atthe spaced apart locations.

A still further aspect of the invention involves a multi-ply sheet thatincludes an embossed base sheet having a back side possessingprojections, adhesive on the back side of the embossed base sheet atspaced apart locations so that portions of the back side of the embossedbase sheet between the projections are devoid of adhesive, and a flatbacking sheet devoid of embossing and adhered to the back side of theembossed base sheet at the spaced apart locations.

Another aspect of the invention involves a method of producing anembossed tissue that involves conveying a base sheet through a nipbetween a first impression roll and a pattern roll to push portions ofthe base sheet into indented portions of the pattern roll, conveying thebase sheet through a nip between the pattern roll and a secondimpression roll made of rubber having a lower hardness than the rubberfrom which the first impression roll is made to push the portions of thebase sheet further into the indented portions of the pattern roll toproduce an embossed tissue.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The foregoing and additional details and features associated with thepresent invention will become more apparent from the following detaileddescription considered with reference to the accompanying drawingfigures in which like elements are designated by like reference numeralsand wherein:

FIG. 1 is a schematic illustration of an apparatus for embossing a paperproduct in accordance with one aspect of the present invention;

FIG. 2 is a front view of the roller arrangement used in the apparatusshown in FIG. 1;

FIG. 3A is a schematic illustration of an alternative arrangement forcarrying out double depth embossing in accordance with the presentinvention;

FIG. 3B is a cross-sectional view of a portion of the interface betweenone of the pattern rolls and one of the impression rolls shown in FIG.3A;

FIG. 3C is a cross-sectional view of a portion of the interface betweenthe other pattern roll and impression roll used in the apparatus shownin FIG. 3A;

FIG. 4A is a schematic illustration of a multi-ply paper productproduced in accordance with the present invention;

FIG. 4B is a schematic illustration of a multi-ply tissue productproduced in accordance with known methods;

FIG. 5 is a schematic illustration of another apparatus for embossing apaper product in accordance with another aspect of the presentinvention;

FIG. 6A is an illustration of one emboss pattern used in conjunctionwith the present invention;

FIG. 6B is an enlarged illustration of one portion of the emboss patternshown in FIG. 6A;

FIG. 7 is an illustration of a different emboss pattern used inconnection with the present invention;

FIG. 8 is an illustration of a further emboss pattern used in connectionwith the present application;

FIG. 9 is a graph of GM tensile strength versus caliper comparing theembossing technique of the present invention versus conventionalembossing;

FIG. 10 is a graph of GM tensile strength versus GMMMD (friction)comparing the embossing technique of the present invention versusconventional embossing;

FIG. 11 is a graph of GM Tensile Strength versus tensile moduluscomparing the embossing technique of the present invention andconventional embossing;

FIG. 12 is a graph of GM tensile strength versus sensory panel softnessfor the present invention and for conventional embossing;

FIG. 13 is a graph of GM tensile strength versus visual test comparingthe embossing technique of the present invention and conventionalembossing;

FIG. 14 is a graph of GM tensile strength versus caliper comparing theembossing technique of the present invention versus conventionalembossing;

FIG. 15 is a graph of GM tensile strength versus GMMMD comparing theembossing technique of the present invention and conventional embossing;

FIG. 16 is a graph of GM tensile strength versus tensile moduluscomparing the embossing technique of the present invention andconventional embossing;

FIG. 17 is a graph of GM tensile strength versus sensory softness valuecomparing the embossing technique of the present invention andconventional embossing;

FIG. 18 a is a magnified cross-section of a multi-ply tissue produced inaccordance with the embossing technique of the present invention;

FIG. 18 b is a magnified cross-sectional view of a multi-ply tissueformed in accordance with conventional embossing;

FIG. 19 a is a magnified cross-sectional view of a multi-ply tissueproduced in accordance with the embossing technique of the presentinvention;

FIG. 19 b is a magnified cross-sectional view of a multi-ply tissueproduced in accordance with conventional embossing;

FIG. 20 a is a magnified cross-sectional view of a multi-ply tissueproduced in accordance with the embossing technique of the presentinvention;

FIG. 20 b is a magnified cross-sectional view of a multi-ply tissueproduced in accordance with conventional embossing;

FIG. 21 a is a magnified cross-sectional view of a multi-ply tissueproduced in accordance with the embossing technique of the presentinvention;

FIG. 21 b is a magnified cross-sectional view of a multi-ply tissueproduced in accordance with conventional embossing;

FIG. 22 is a graph of GM tensile illustrating the effect of differentrubber hardness of the impression roll;

FIG. 23 is a graph of GM tensile strength versus tensile modulusillustrating the effect of different rubber hardness of the impressionroll;

FIG. 24 is a graph of GM tensile strength versus GMMMD illustrating theeffect of rubber hardness of the impression roll on the tissue product;

FIG. 25 is a graph of GM tensile strength versus sensory panel softnessillustrating the effect of rubber hardness of the impression roll on thetissue product formed in accordance with the present invention;

FIG. 26 is a graph of GM tensile strength versus caliper illustratingthe effect of adhesive on a tissue product produced in accordance withthe embossing technique of the present invention;

FIG. 27 is a graph of GM tensile strength versus tensile modulusillustrating the effect of adhesive on the tissue product produced inaccordance with the embossing technique of the present invention;

FIG. 28 is a graph of GM tensile strength versus GMMMD illustrating theeffect of adhesive on the tissue product produced in accordance with theembossing technique of the present invention;

FIG. 29 is a graph of GM tensile strength versus sensory panel softnessillustrating the effect of adhesive on the tissue product produced inaccordance with the embossing technique of the present invention;

FIG. 30 is a graph of GM tensile strength versus caliper illustratingthe effect of adhesive on the tissue product produced using theembossing technique of the present invention;

FIG. 31 is a graph of GM tensile strength versus tensile modulusillustrating the effect of adhesive on the tissue product produced inaccordance with the embossing technique of the present invention;

FIG. 32 is a graph of GM tensile strength versus GMMMD illustrating theeffect of adhesive on a tissue product produced in accordance with theembossing technique of the present invention;

FIG. 33 is a graph of GM tensile strength versus sensory panel softnessillustrating the effect of adhesive on a tissue product produced inaccordance with the embossing technique of the present invention;

FIG. 34 is a graph of GM tensile strength versus caliper illustratingthe effect of the emboss pattern and emboss process of the presentinvention on a two-ply tissue product;

FIG. 35 is a graph of GM tensile strength versus tensile modulusillustrating the effect of the emboss pattern and the emboss process ofthe present invention on the fabrication of a two-ply tissue product;

FIG. 36 is a graph of GM tensile strength versus GMMMD illustrating theeffect of the emboss pattern and the emboss process of the presentinvention on fabrication of a two-ply tissue product;

FIG. 37 is a graph of GM tensile strength versus sensory panel softnessillustrating the effect of the emboss pattern and the emboss process ofthe present invention on the fabrication of a two-ply tissue product;

FIG. 38 is a graph of GM tensile strength versus caliper illustratingthe effect of emboss pattern on a tissue product produced in accordancewith the emboss technique of the present invention;

FIG. 39 is a graph of GM tensile strength versus tensile modulusillustrating the effect of the emboss pattern and the emboss process onthe fabrication of a two-ply tissue product;

FIG. 40 is a graph of GM tensile strength versus GMMMD illustrating theeffect of emboss pattern on a tissue product produced in accordance withthe emboss technique of the present invention;

FIG. 41 is a graph of GM tensile strength versus sensory panel softnessillustrating the effect of the emboss pattern and the emboss process onthe fabrication of a two-ply tissue product;

FIG. 42 is a graph of GM tensile strength versus caliper illustratingthe effect of steam preconditioning on the production of a two-plytissue product in accordance with the embossing technique of the presentinvention;

FIG. 43 is a graph of GM tensile strength versus tensile modulusillustrating the effect of steam preconditioning on the fabrication of atwo-ply tissue product in accordance with the embossing technique of thepresent invention;

FIG. 44 is a graph of GM tensile modulus versus GMMMD illustrating theeffect of steam preconditioning on the fabrication of a two-ply tissueproduct produced using the embossing technique of the present invention;

FIG. 45 is a graph of GM tensile strength versus sensory softnessillustrating the effect of the emboss pattern used in the prior art on atwo-ply tissue product using various emboss;

FIG. 46 is a graph of GM tensile strength versus GMMMD illustrating theeffect of the emboss pattern used in the prior art on the production ofa two-ply tissue product using different emboss techniques;

FIG. 47 is a graph of GM tensile strength versus caliper illustratingthe effect of the emboss pattern used in the prior art on thefabrication of a two-ply tissue product using different embosstechniques;

FIG. 48 is a graph of GM tensile strength versus GM tensile modulusillustrating the effect of the emboss pattern used in the prior art onthe fabrication of a two-ply tissue product using different embosstechniques;

FIG. 49 is a schematic illustration of an apparatus used to impress apattern on a multi-ply paper product in accordance with another aspectof the invention;

FIG. 50 is an enlarged cross-sectional view of a portion of a multi-plyproduct produced using the apparatus shown in FIG. 49;

FIG. 51 is an enlarged cross-sectional view of a portion of anothermulti-ply product produced in accordance with the present invention;

FIG. 52 is a schematic illustration of an apparatus used to produce atwo-ply tissue product having a heavily embossed pattern in accordancewith another aspect of the invention;

FIG. 53 is a side view of a portion of a tissue product having adifferent depth or double depth emboss pattern;

FIG. 54 is a schematic illustration of an apparatus used to produce aone ply tissue product in accordance with another aspect of theinvention; and

FIG. 55 is a schematic illustration of an apparatus used to produce aone ply tissue product in accordance with another aspect of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Generally speaking, one aspect of the present invention relates to amulti-ply absorbent paper product possessing what is termed adifferential depth emboss that contributes to imparting highly desirablecharacteristics and properties to the multi-ply paper product. One ofthe plies forming the multi-ply paper product is embossed relativelyheavily while the other ply is relatively lightly embossed. By embossingone ply more heavily than the other, the resulting multi-ply paperproduct possesses better perceived softness and bulk along with betteremboss definition, yet the strength of the resulting multi-ply paperproduct is not unduly degraded. The preservation of product strengthresults from less emboss damage of the lightly embossed ply. Inaccordance with the present invention, the differential depth embossmaintains a good emboss definition on the outside of the multi-ply paperproduct by virtue of the heavily embossed ply while at the same timereducing the backside friction. The differential depth embossing processdeeply embosses the top ply first through higher penetration depth orhigher nip pressure. The top ply is then joined to or nested with thebottom ply through a second nip which imparts shallower embossingthrough lower penetration depth or lower nip pressure.

The improved properties and characteristics of the multi-ply paperproduct associated with the present invention is also achieved by usingthe differential depth embossing in conjunction with an embossingpattern having particular characteristics. When the first and secondplies are nested together, the plies become contact laminated to oneanother so that the primary adhesion between the sheets is the result ofcontact between cellulosic fibers rather than through an intermediateadhesive. The embossed pattern is specifically designed to avoidnon-elongated sharply defined contact regions as it has been foundthrough developmental efforts that contact regions having thesecharacteristics produce a rather harsh feeling sheet. In the presentinvention, the embossed pattern is configured so that the contact regionis either elongated and sharply defined (having a small radius ofcurvature along the edge between the emboss and the background) ornon-elongated and gently rounded. The voids defined by these contactregions are thus compliant. The combination of the differential depthembossing and the particular characteristics of the embossed patterntogether results in a multi-ply paper product such as tissue paperhaving significantly increased softness and puffiness characteristics,and improved bulk and emboss definition as compared to other knowntissue products while at the same time possessing strengthcharacteristics not commonly found in tissue paper having suchattributes.

The present invention as described in more detail below has applicationto multi-ply paper products in which characteristics such as aresoftness, puffiness, bulk and emboss definition contribute to perceivedproduct desirability. The paper products include absorbent paper,bathroom and facial tissue, napkins and towels. The detailed descriptionset forth below makes reference to tissue paper, but it is to beunderstood that the present invention is equally applicable to theseother types of multi-ply paper products.

The multi-ply tissue product according to the present invention isfabricated using the apparatus shown in FIG. 1. To produce thedifferential depth embossed tissue, a first tissue ply 20 is conveyedpast a series of idler rollers 22 towards the nip that is locatedbetween a pattern roll 24 which may be made of steel and an impressionroll 26 which may be made of rubber. The pattern roll 24 rotates in theclockwise direction while the impression roll 26 rotates in thecounterclockwise direction. The first tissue ply 20 forms the bottom plyin the resulting multi-ply tissue.

A second tissue ply 28 is conveyed around an idler roller 32 and is thenpassed into a nip located between an impression roll 34 which may bemade of rubber and the pattern roll 24. The second tissue ply 28 isadapted to form the top ply in the resulting multi-ply tissue. Thesecond tissue ply 28 is rewound around the pattern roll 24 to form theoutside of the multi-ply tissue. As the second tissue ply 28 passesthrough the nip between the pattern roll 24 and the impression roll 34,the second tissue ply 28 is heavily embossed. This heavy embossing ofthe second tissue ply imparts a high degree of emboss definition andperceived puffiness to the second tissue ply 28.

In contrast, the first tissue ply 20 that is fed through the nip betweenthe pattern roll 24 and the impression roll 26 is only lightly embossed.That is, the first tissue ply is embossed to a lesser degree than thesecond tissue ply 28. The lightly embossed first tissue ply 20 is joinedto or nested with the heavily embossed second tissue ply 28 at the nipbetween the pattern roll 24 and the impression roll 26. By virtue ofbeing rewound on the pattern roll 24 and joined to the first tissue ply,the relatively high friction on the heavily embossed second tissue ply28 faces towards the lightly embossed first tissue ply 20. By virtue ofthe relatively light embossing that occurs at the nip between thepattern roll 24 and the impression roll 26, the bottom side or inside ofthe two-ply tissue possesses a relatively low friction and thus a betterperceived softness. The resulting multi-ply tissue exiting from the nipbetween the pattern roll 24 and the impression roll 26 is passed arounda series of idler rolls 36 and is then wound on a take-up roll (notshown).

As mentioned above, the second tissue ply 28 is rather heavily embossedwhereas the first tissue ply 20 is rather lightly embossed. Thisdifference in the degree of embossment can be achieved in several ways.For example, the impression rolls 26, 34 can be made of materials havingdifferent degrees of softness to allow a higher penetration depth in thecase of the nip between the pattern roll 24 and the impression roll 34as compared to the nip between the pattern roll 24 and the impressionroll 26. Alternatively, greater pressure can be applied at the nipbetween the pattern roll 24 and the impression roll 34 as compared tothe nip between the pattern roll 24 and the impression roll 26. With theuse of more pressure to achieve the different penetration depth, theimpression rolls 26, 34 can have the same hardness or softnesscharacteristics (e.g., 40-80 Shore Durometer A).

FIG. 2 illustrates the emboss roll 24 situated between the twoimpression rolls 26, 34. FIG. 2 also illustrates one example of thepattern on the pattern roll 24 that has been found to produce, inconjunction with the differential depth emboss described above,multi-ply paper products such as tissues having better perceivedsoftness and bulk along with better emboss definition yet without undulydegrading the strength of the multi-ply tissue. The characteristics ofthe emboss pattern and the way in which such characteristics contributeto the overall advantageous attributes of the multi-ply tissue will bediscussed in more detail below.

FIG. 3A illustrates a slightly modified form of the apparatus forcarrying out the differential depth embossing. Here, the first tissueply 20 is fed from an unwinder 40 to the nip located between animpression roll 42 which may be made of rubber and a first pattern roll44 which may be made of steel. The first tissue ply 20 is lightlyembossed as it passes through the nip between the impression roll 42 andthe first pattern roll 44. At the same time, the second tissue ply 28 isfed from an unwinder 46 towards the nip located between an impressionroll 48 which may be made of rubber and a second pattern roll 50 whichmay be made of steel. The nip between the impression roll 48 and thesecond pattern roll 50 is designed to impart a heavy emboss to thesecond tissue ply 28.

FIG. 3B illustrates that the light emboss can be achieved by allowingthe engravings on the first pattern roll 44 to penetrate into theimpression roll 42 to a lesser extent as compared to the heavy embossthat is applied to the second tissue ply 28. This can be accomplished byusing less pressure or by using an impression roll 42 made of a materialthat is not as easily penetrated as the impression roll 48, and/or byusing a pattern roll 44 less engraved than the pattern roll 50. As shownin FIG. 3C, the heavy emboss applied to the second tissue ply 28 can beachieved by the engravings on the pattern roll 50 penetrating moredeeply into the impression roll 48 through the use of greater pressureof a softer material for the impression roll 48, and/or deeperembossment on the pattern roller 50.

After the heavily embossed second tissue ply 28 passes through the nipbetween the impression roll 48 and the pattern roll 50, a gluing unit 52applies glue to the projections that are formed on the exterior surfaceof the embossed second tissue ply 28 by virtue of the embossing. Theheavily embossed second tissue ply 28 with the applied glue thenadvances further to a nip between the pattern roll 44 and the patternroll 50. At this point, the lightly embossed first tissue ply 20 isnested with the heavily embossed second tissue ply 28 and are thenconveyed around a marrying roll 54 and subsequently wound.

FIG. 4A generally illustrates the multi-ply tissue that results from thedifferential depth embossing technique illustrated in FIG. 3A. Forcomparison purposes, FIG. 4B illustrates a conventional multi-ply tissueformed by conveying two tissue plies through the nip formed between asteel engraved roll and a rubber roll. As can be seen, the two tissuesforming the conventional multi-ply tissue are deeply nested within oneanother. In this conventional multi-ply tissue, the tissue may possessdesirable emboss definition and perceived puffiness characteristics, butthe tissue will be rather rough. In contrast, in the multi-ply tissue ofthe present invention as shown in FIG. 4A, the tissue will not onlypossess better perceived softness and bulk along with better embossdefinition, but will also possess desirable strength characteristics byvirtue of the lightly embossed first tissue ply 20.

FIG. 5 illustrates another variation on the apparatus shown in FIG. 1.In this version shown in FIG. 5, two preconditioning mechanisms 60, 62are provided for preconditioning each of the tissue plies 20, 28 priorto entering the respective nips. The preconditioning mechanisms 60, 62are designed to impart moisture and/or heat to the tissue plies 20, 28.The preconditioning mechanisms 60, 62 can be designed to apply moistureand heat to the tissue plies 20, 28 at the same time or can be designedto individually apply steam or moisture and heat to the tissue plies 20,28 in successive stages. As a further alternative, the preconditioningmechanisms 60, 62 can be designed to apply only moisture or only heat tothe tissue plies 20, 28. In a preferred form of the invention, thepreconditioning mechanisms 60, 62 are in the form of steam showers thatapply a combination of moisture and heat to the tissue plies 20, 28.

A first one of the preconditioning mechanisms 60 is positioned upstreamof the nip located between the pattern roll 24 and the impression role26 and a second one of the preconditioning mechanisms 62 is positionedupstream of the nip located between the pattern roll 24 and theimpression roll 34. An additional idler roll 56 is also provided at theposition shown in FIG. 5. The second tissue ply 28 is conveyed aroundthis idler roll 56 prior to being subjected to the preconditioningtreatment (i.e., moisture and/or heat) by the second preconditioningmechanism 62.

Although the arrangement shown in FIG. 5 has been found advantageousfrom the standpoint of enhancing product quality, other methods andarrangements for applying moisture and heat (e.g., steam) to the tissueplies 20, 28 that are known to skilled artisans can be employed and fallwithin the scope of the present invention. By way of example, steam canbe applied to either or both sides of the plies 20, 28, and steam can beapplied to the ply 28 ahead of the idler roller 56. Also, the idlerroller 56 shown in FIG. 5 is not necessary for practicing the inventionwhen steam is applied to the tissue ply 28 at a point between the idlerroll 32 and the impression roll 34.

The arrangement shown in FIG. 5 has been found to be quite advantageousin that steam preconditioning each of the tissue plies 20, 28 prior toembossing provides a much higher caliper and lower tensile modulus ascompared to tissue plies not subjected to steam preconditioning. Withoutbeing bound by theory, it is believed that preconditioning one or bothof the plies with steam enables the plies to become more compliant andthis allows an improved emboss definition to be imparted to the web.Better emboss definition is highly desirable as it helps enhance sheetcaliper.

As mentioned above, the present invention is based on the discovery thatunexpectedly advantageous results can be achieved by combiningdifferential depth emboss with an emboss pattern having certaincharacteristics. FIGS. 6A, 7 and 8 illustrate three different embosspatterns that, in combination with the differential depth emboss,provide particularly advantageous results.

The emboss pattern 70 shown in FIG. 6A is in the form of a series ofspaced apart flowers 72. The pattern also includes dots arranged in theshape of diamonds, at least some of which surround the flowers 72. Eachof the flowers 72 is defined by emboss elements 74, substantially all ofwhich are elongated in shape. FIG. 6B illustrates an enlarged version ofone of the elongated emboss elements 74′. As can be seen, the elongatedemboss element 74′ is dimensioned so that the dimension y issignificantly greater than the dimension x. The emboss element thuspossesses an aspect ratio (i.e., y/x) greater than 1 (if the dimensionsx and y were equal, the aspect ratio would be 1). The aspect ratio ofthe emboss element is preferably between about 1 and about 10,preferably greater than about 2. Without being bound by theory, it isbelieved that using emboss elements with aspect ratios betweenapproximately 1 and approximately 10, greater than approximately 2provides a smoother and puffier structure that is pleasing to the touchand thus perceived to be of softer quality.

FIG. 7 illustrates another preferred emboss pattern 80. Here, the embosspattern is in the form of alternating and spaced apart flowers 72, likethose shown in FIG. 6A, and hearts 82. The hearts provide an open embosspattern. The aspect ratio of an individual heart is the contact areaweight average of the individual aspect ratios of the components makingup the heart. The pattern shown in FIG. 7 also includes dots arranged inthe form of diamonds, with each diamond shaped arrangement of dotssurrounding one of the flowers 72 and hearts 82.

FIG. 8 illustrates another preferred emboss pattern 90. Here, the embosspattern is in the form of alternating and spaced apart flowers 72, likethose shown in FIG. 6A, and double hearts 92 defined by a heart shapedemboss positioned within another heart shaped emboss. The patternfurther includes dots likes those shown in FIG. 7 that are arranged inthe form of diamonds each surrounding one of the flowers and doublehearts. The double hearts provide an open emboss pattern. The aspectratio of an individual double heart is the contact area weight averageof the individual aspect ratios of the components making up the doubleheart.

A variety of tests were conducted on different tissue samples producedaccording to the differential depth emboss (DDE) of the presentinvention and tissue samples produced according to the conventionalprocess in which two tissue plies are conveyed between a steel/rubbernip. The tests are discussed below, with the resulting data beingsummarized in various graphs and tables set forth below and in thedrawing figures.

EXAMPLE 1

This example provides a comparison between tissue product convertedusing the conventional emboss process and that converted using thedifferential depth embossing process. Tissue base sheets were made on acrescent former pilot paper machine using 15 degree bevel at a percentcrepe of 22%. The base sheet furnish contains 65% Southern hardwoodkraft and 35% Northern softwood kraft. Base sheets were converted totwo-ply tissue using the conventional steel-to-rubber process and thedifferential depth emboss process. The rubber rolls with hardness 40Shore Durometer A were used in both processes. Both processes used thesame emboss pattern shown in FIG. 7. Each process converted base sheetsat three or four penetration depths (or nip pressures). Physicalproperties of various tissue products were measured and compared. FIGS.9-13 show the test results. It can be seen from FIG. 9 that thedifferential depth emboss process made product with slightly lowercaliper at equal GM tensile strength (geometric mean strength which isequal to the square root of the product obtained by the multiplying MDdry tensile and CD dry tensile) than those converted using theconventional emboss process. FIG. 10 shows that the differential depthemboss process resulted in product with lower friction or GMMMD(friction deviation from the mean) at equal GM tensile strength. Thedifferential depth emboss process produced product with higher tensilemodulus at equal GM tensile strength as shown in FIG. 11. The hightensile modulus is caused by light embossing on the bottom ply. FIG. 12shows that the differential depth emboss process made product withbetter sensory softness at equal GM tensile strength. Compared to theconventional product, the overall softness value of the differentialdepth embossing product is 0.4 or more units higher which is significantat the 95% confidence level. The visual tests were performed on selectedprototypes. The results indicate that the differential depth embossprocess produced product with better visual perception at equalpenetration depth as shown in FIG. 13.

EXAMPLE 2

This example compares and illustrates the differences between thedifferential depth emboss product and the conventional tissue product.Tissue base sheets were made from a furnish containing 60% Southernhardwood kraft, 30% Northern softwood kraft and 10% Broke. Base sheetswere made with square blade at 20% crepe ratio and converted intotwo-ply tissue using the conventional process and the differential depthemboss process. The hardness of rubber rolls used in both processes is40 Shore Durometer A. Both processes used the same emboss patterncorresponding to the emboss pattern shown in FIG. 8. Each processconverted base sheets at two penetration depths (or nip pressures). Thebasis weight of two-ply tissue product is 17 to 20 lbs/3000 square ft.Physical test results are plotted in FIGS. 14-16. FIGS. 14 and 15indicate that two-ply tissue converted using the differential depthemboss process has higher caliper and lower friction at equal GM tensilestrength than that converted using the conventional process. FIG. 16shows that the differential depth embossing product has higher tensilemodulus than the conventional product. The sensory softness result isshown in FIG. 17. The differential depth emboss product has a overallsoftness value 0.2 to 0.4 units higher than the conventional product.

EXAMPLE 3

This example illustrates the effect of the emboss process on two-plytissue. The furnish of tissue base sheets contains 30% Northern softwoodkraft, 60% Southern hardwood kraft and 10% trial broke. Base sheets weremade at basis weight of 9.3 lbs/3000 square ft using a square crepeblade at 72 degrees creping angle. The conventional process and thedifferential depth emboss process were used to converted base sheet totwo-ply tissue. The rubber rolls with hardness 40 Shore Durometer A wereused in both processes. The same emboss pattern used in Example 2 abovewas used in this example. Two-ply tissue was converted using theconventional emboss process at penetration depth 0.085 inches. Fortwo-ply tissue converted using the differential depth emboss process,the penetration depth is 0.095 inches for top ply (or outside) and thenthe top and bottom (or inside) plies are embossed together atpenetration depth 0.065 inches.

Table 1 below lists all of the physical properties and sensory softnessvalues for the differential depth embossing tissue product and thetissue product produced using the conventional method. The way in whichthe properties and values shown in FIG. 1, as well as subsequent tables,are obtained is known in the art and so a detailed description is notprovided here.

Compared to the conventional emboss product, the differential depthemboss product has higher caliper, higher tensile modulus, and lowerfriction. The differential depth emboss product has a overall sensorysoftness value 0.74 units higher than the conventional emboss product.The difference in softness value is 0.4 units or more which issignificant at 95% confidence level.

TABLE 1 Physical Properties of Two-Ply Tissue Products ConventionalDifferential Depth Emboss Product Emboss Product Basis Weight (lbs/ream)18.1 18.4 Caliper (0.001″/8st) 78.3 84.8 MD Dry Tensile (g/3″) 990 934CD Dry Tensile (g/3″) 421 430 GM Dry Tensile (g/3″) 646 634 TensileModulus (g/% strain) 19.4 20.5 Friction 0.189 0.181 Roll Diameter (inch)4.42 4.56 Roll Compressibility (%) 19.1 19.7 Sensory Softness 16.8917.63

EXAMPLE 4

This example compares and illustrates the differences between thedifferential depth emboss tissue product and the conventional product.Tissue base sheets similar to those used in the example 3 were convertedto 2-ply tissue. An emboss pattern similar to that illustrated in FIG. 8was used in the present example. The rubber rolls with hardness 40 ShoreDurometer A were used in both processes. Two-ply tissue was convertedusing the conventional emboss process at penetration depth 0.080 inches.For two-ply tissue converted using the differential depth embossprocess, the penetration depth is 0.090 inches for top ply and then thetop and bottom plies are embossed together at a penetration depth of0.060 inches. The physical properties of the tissue products weremeasured and compared. Table 2 below lists all of test results includingsensory softness value. Compared to the conventional emboss product, thedifferential depth emboss product has higher caliper, higher tensilemodulus, and lower friction. Also, the differential depth emboss producthas a sensory softness value 0.4 units higher than the conventionalemboss product.

TABLE 2 Physical Properties of Two-Ply Tissue Products ConventionalDifferential Depth Emboss Product Emboss Product Basis Weight (lbs/ream)18.4 18.7 Caliper (0.001″/8st) 74.5 78.3 MD Dry Tensile (g/3″) 1044 1075CD Dry Tensile (g/3″) 432 447 GM Dry Tensile (g/3″) 672 693 TensileModulus (g/% strain) 20.2 24.3 Friction 0.172 0.158 Roll Diameter (inch)4.33 4.46 Roll Compressibility (%) 19.2 19.6 Sensory Softness 17.3517.75

EXAMPLE 5

This example illustrates that the effect of the emboss process ontwo-ply tissue. The furnish of tissue base sheet contains 30% Northernsoftwood kraft, 60% Southern hardwood kraft, and 10% trial broke. Anemboss pattern similar to that shown in FIG. 8 was used in the presentexample. Two-ply tissue was converted using the conventional embossprocess at a penetration depth of 0.095 inches. For two-ply tissueconverted using the differential depth emboss process, the penetrationdepth is 0.090 inches for top ply and then top and bottom plies wereembossed together at a penetration depth of 0.065 inches. Rubber rollswith hardness 40 Shore Durometer A were used in both processes. Table 3below lists all of test results including sensory softness value.

Compared to the conventional emboss product, the differential depthemboss product has higher tensile modulus, and lower friction. Bothproducts have similar caliper. The differential depth emboss product hasa sensory softness value 0.68 units higher than the conventional embossproduct. Thus, the difference in softness value is greater than 0.4units which is significant at 95% confidence level.

TABLE 3 Properties of Two-Ply Tissue Products Conventional DifferentialDepth Emboss Product Emboss Product Basis Weight (lbs/ream) 18.6 18.8Caliper (0.001″/8st) 72.9 73 MD Dry Tensile (g/3″) 1129 1111 CD DryTensile (g/3″) 438 455 GM Dry Tensile (g/3″) 703 711 Tensile Modulus(g/% strain) 21.15 24.75 Friction 0.161 0.144 Roll Diameter (inch) 4.314.25 Roll Compressibility (%) 19.7 20 Sensory Softness 17.55 18.23

EXAMPLE 6

This example illustrates that the effect of adhesive and the embossprocess on two-ply tissue. Tissue base sheets similar to those used inExample 5 were converted using both the differential depth embossprocess and the conventional process. The rubber rolls with hardness 40Shore Durometer A were used in both processes. Both processes used thesame emboss pattern similar to that shown in FIG. 8. Two strips ofadhesive per embossed sheet at 4.5 mg/linear meter per strip wereapplied on the back side of the top ply to improve the ply-bond. For thedifferential depth embossing process, the two-ply tissue with adhesiveapplied was embossed at a penetration depth of 0.090 inches for the topply, and then the top and bottom plies were embossed together at apenetration depth of 0.060 inches. A two-ply tissue converted using theconventional emboss process was embossed at a penetration depth of 0.085inches. Compared to the conventional product, the differential depthembossing product has higher caliper, higher tensile modulus and higherfriction. Higher friction for the differential depth embossing productis inconsistent with the results observed in previous examples. Thesensory softness result indicates that the differential depth embossingproduct and the conventional product have similar softness. Based onphysical attributes and softness results, applying adhesive for runningthe differential depth embossing process is not preferred.

TABLE 4 Properties of Two-Ply Tissue Products Conventional DifferentialDepth Emboss Product Emboss Product (with Glue Applied) (with GlueApplied) Basis Weight (lbs/ream) 17.9 18.0 Caliper (0.001″/8st) 75.780.0 MD Dry Tensile (g/3″) 1001 965 CD Dry Tensile (g/3″) 444 430 GM DryTensile (g/3″) 667 644 Perf. Tensile (g/3″) 434 410 Tensile Modulus (g/%strain) 20.6 23.4 Friction 0.175 0.189 Roll Diameter (inch) 4.29 4.40Roll Compressibility (%) 18.9 20.5 Sensory Softness 17.0 17.16

EXAMPLE 7

This example illustrates the effect of adhesive on two-ply tissueconverted using the differential depth emboss process. Tissue basesheets similar to those used in Example 5 were converted to two-plytissue using the differential depth emboss process. An emboss patternsimilar to that shown in FIG. 8 was used in the present example. Therubber rolls with hardness 40 Shore Durometer A were used. Two strips ofadhesive per embossed sheet at 4.5 mg/linear meter per strip wereapplied on the top ply. The differential depth embossing product withadhesive applied was embossed at a penetration depth of 0.090 inches forthe top ply, and then the top and bottom plies were embossed together ata penetration depth of 0.060 inches. The differential depth embossingproduct without adhesive applied was embossed at a penetration depth of0.095 inches for the top ply and embossed at a penetration depth of0.065 inches as the top and bottom plies were joined together. Table 5below lists the physical attributes and softness value results. Theeffect of adhesive on the perforated tensile strength of two-ply tissueis not significant. The differential depth embossing product withoutglue applied has higher caliper, lower tensile modulus and lowerfriction. Based on sensory softness results, the differential depthembossing product without adhesive applied is softer than that withadhesive applied. The difference in sensory softness value is greaterthan 0.4 units which is significant at the 95% confidence level. Asmentioned in the Example 6, the adhesive is not preferred when runningthe differential depth emboss process.

TABLE 5 Properties of Two-Ply Tissue Products Differential Depth EmbossProduct Differential Depth (with Glue Applied) Emboss Product BasisWeight (lbs/ream) 18.01 18.5 Caliper (0.001″/8st) 80.0 81.8 MD DryTensile (g/3″) 965 1034 CD Dry Tensile (g/3″) 430 424 GM Dry Tensile(g/3″) 644 662 Perf. Tensile (g/3″) 404 410 Tensile Modulus (g/% strain)23.4 21.7 Friction 0.189 0.176 Roll Diameter (inch) 4.40 4.53 RollCompressibility (%) 20.5 20.3 Sensory Softness 17.18 17.85

EXAMPLE 8

This example illustrates that the effect of the emboss process ontwo-ply tissue. Tissue base sheet was made using undulatory crepingblades. The blade was undulated at a spacing of 20 undulations/inch anda depth of 0.020″ and had a 25 degree bevel angle. The furnish of basesheet was 30% Northern softwood kraft, 60% Southern hardwood kraft, and10% trial broke. The rubber rolls with hardness 40 Shore Durometer Awere used in both processes. Two-ply tissue converted using theconventional emboss process was embossed at a penetration depth of 0.095inches. For two-ply tissue converted using the differential depth embossprocess, the penetration depth was 0.095 inches for the top ply, andthen the top and bottom plies were embossed together at a penetrationdepth of 0.065 inches. An emboss pattern similar to that shown in FIG. 8was employed in the present example. Table 6 below lists all of thephysical properties and sensory softness value. Compared to theconventional product, the differential depth emboss product has lowercaliper, higher tensile modulus, and lower friction. The differentialdepth emboss product has an overall sensory softness value 0.65 unitshigher than the conventional embossing product. The difference insensory softness value is greater than 0.4 units which is significant atthe 95% confidence level.

TABLE 6 Physical Properties of Two-Ply Tissue Products ConventionalDifferential Depth Emboss Product Emboss Product Basis Weight (lbs/ream)18.4 18.6 Caliper (0.001″/8st) 71.3 69.2 MD Dry Tensile (g/3″) 1043 1001CD Dry Tensile (g/3″) 441 456 GM Dry Tensile (g/3″) 678 676 TensileModulus (g/% strain) 19.81 22.18 Friction 0.154 0.149 Roll Diameter(inch) 4.23 4.16 Roll Compressibility (%) 21.5 18.5 Sensory Softness17.62 18.27

EXAMPLE 9

This example illustrates that the effect of emboss process on stratifiedtissue base sheet with basis weight ranging from 11 to 13 lbs/3000square ft. Tissue base sheet is in stratified mode and the layer splitof base sheet was 65% (100% Northern hardwood kraft) to the Yankee sideand 35% (100% Northern softwood kraft) to the air side. Base sheets wereconverted to two-ply tissue using an emboss pattern similar to thatillustrated in FIG. 8. The rubber rolls with hardness 40 Shore DurometerA were used in both processes. Two-ply tissue was converted using theconventional emboss process at penetration depth 0.095 inches. Fortwo-ply tissue converted using the differential depth emboss process,the penetration depth was 0.100 inches for the top ply, and then the topand bottom plies were embossed together at a penetration depth of 0.065inches. Table 7 below lists all of the test results including sensorysoftness value. Compared to the conventional product, the differentialdepth embossing product has lower friction and higher caliper at thesimilar GM tensile strength. The differential depth embossing producthas lower tensile modulus which differs from previous examples. Thedifferential depth emboss product has a better sensory softness (20.44vs. 20.24 units).

TABLE 7 Physical Properties of Two-Ply Tissue Products DifferentialDepth Conventional Emboss Product Emboss Product (40/80 Sha) Pene. Depth(×0.001″) 95 100/65 Basis Weight (lbs/ream) 26.5 26.4 Caliper(0.001″/8st) 105.7 112.2 MD Dry Tensile (g/3″) 960 921 CD Dry Tensile(g/3″) 412 381 GM Dry Tensile (g/3″) 629 592 Tensile Modulus (g/%strain) 14.1 13.86 Friction 0.168 0.162 Sensory Softness 20.24 20.44

EXAMPLE 10

This example illustrates the effect of the emboss process on homogeneoustissue base sheet with basis weight ranging from 11 to 13 lbs/3000square feet. Base sheets were in the homogeneous mode containing 35%Northern softwood kraft and 65% Northern hardwood kraft. Base sheetswere converted to two-ply tissue using an emboss pattern similar to thatshown in FIG. 8. Rubber rolls with hardness 40 Shore Durometer A wereused in both processes. Two-ply tissue was converted using theconventional emboss process at a penetration depth 0.100 inches. Fortwo-ply tissue converted using the differential depth emboss process,the penetration depth was 0.100 inches for the top ply, and then the topand bottom plies were embossed together at a penetration depth of 0.065inches. Table 8 below lists all of the test results including sensorysoftness value. Compared to the conventional product, the differentialdepth emboss product has lower friction and higher caliper at equal GMtensile strength. The differential depth embossing product has lowertensile modulus which is consistent with the results in example 9. Thedifferential depth emboss product has a better sensory softness valuethat is 0.56 units higher than the conventional products.

TABLE 8 Physical Properties of Two-Ply Tissue Products DifferentialDepth Conventional Emboss Product Emboss Product (40/80 Sha) Pene. Depth(×0.001″) 100 100/65 Basis Weight (lbs/ream) 26.5 26.8 Caliper(0.001″/8st) 104.6 108.6 MD Dry Tensile (g/3″) 1097 1046 CD Dry Tensile(g/3″) 426 447 GM Dry Tensile (g/3″) 684 683 Tensile Modulus (g/%strain) 17.13 16.52 Friction 0.177 0.175 Sensory Softness 19.19 19.75

EXAMPLE 11

This example compares and illustrates the differences between themicrostructure between the differential depth emboss product and theconventional tissue product. The base sheet furnish contained 65%Southern hardwood kraft and 35% Northern softwood kraft. Two-ply tissuewas converted using the conventional emboss process at a penetrationdepth of 0.075 inches. For the differential depth embossing product, thepenetration depth was 0.085 inches for the top ply, and then the top andbottom plies were embossed together at a penetration depth of 0.050inches. Both processes used the same emboss pattern depicted in FIG. 7.The rubber rolls with hardness 40 Shore Durometer A were used in bothprocesses. FIGS. 18 a, 18 b and 19 a, 19 b are cross-sectional viewstaken at two different places of products produced conventionally andaccording to the present invention. The illustrations in FIGS. 18 a, 18b and 19 a, 19 b are magnified at 50×. Compared to the cross-sectionalstructure of the conventional product, the bottom ply of thedifferential depth embossing product possesses less curvature because ofthe light emboss as the top and bottom plies are joined together. Basedon the physical test results listed in Table 9 below, less curvatureexplains that the differential depth embossing product has much lowerfriction than the conventional product. The contours of the top ply forboth the differential depth embossing product and the conventionalproduct are similar. The differential depth embossing product canmaintain an emboss definition as good as the conventional product. Thesoftness pocket between the top and bottom plies for the differentialdepth embossing product is larger than that for the conventionalproduct. The larger softness pocket can improve puffiness feel which mayprovide a two-ply tissue with better softness. Based on sensory softnessresults, the differential depth embossing product has better sensorysoftness than the conventional product. The differential depth embossingproduct has larger softness pocket between plies and less curvature onthe bottom ply which contribute better softness and lower friction. Inprevious examples, the differential depth embossing product always haslower friction and better sensory softness than the conventionalproduct.

TABLE 9 Physical Properties of Two-Ply Tissue Products DifferentialDepth Conventional Emboss Product Emboss Product (40/40 Sha) Pene. Depth(×0.001″) 75 85/50 Basis Weight (lbs/ream) 18.95 18.94 Caliper(0.001″/8st) 64.2 67.0 MD Dry Tensile (g/3″) 1127 1154 CD Dry Tensile(g/3″) 518 541 GM Dry Tensile (g/3″) 764 790 Tensile Modulus (g/%strain) 24.5 25.42 Friction 0.152 0.139 Sensory Softness 17.1 18.0

EXAMPLE 12

This example compares microstructure between the differential depthemboss product and the conventional tissue product. Tissue base sheetswere made from a furnish containing 60% Southern hardwood kraft, 30%Northern softwood kraft and 10% Broke and with square blade at 20% creperatio. Two-ply tissue was converted using the conventional embossprocess at a penetration depth of 0.085 inches. For the differentialdepth embossing product, the penetration depth was 0.100 inches for thetop ply, and then the top and bottom plies were embossed together at apenetration depth of 0.065 inches. The rubber roll hardness used in bothprocesses was 40 Shore Durometer A. Both processes used the same embosspattern illustrated in FIG. 8. Table 10 below lists the physicalproperties and sensory softness results. FIGS. 20 a, 20 b and 21 a, 21 bshow the cross-sectional structure taken at two different positions. Theillustrations in FIGS. 20 a, 20 b and 21 a, 21 b are magnified at 50×.The gap (or softness pocket) between top and bottom for the differentialdepth embossing product is much larger than that for the conventionalproduct. Because of the wider softness pocket, the differential depthembossing product has a higher caliper than that of the conventionalproduct. The larger gap between the top and bottom plies can alsoimprove tissue softness. As can be seen from table 10 below, thedifferential depth embossing product has higher softness than theconventional product. The results are consistent with those observed inthe example 11.

TABLE 10 Physical Properties of Two-Ply Tissue Products DifferentialDepth Conventional Emboss Product Emboss Product (40/40 Sha) Pene. Depth(×0.001″) 85 100/65 Basis Weight (lbs/ream) 17.65 18.2 Caliper(0.001″/8st) 72.3 79.2 MD Dry Tensile (g/3″) 929 894 CD Dry Tensile(g/3″) 411 415 GM Dry Tensile (g/3″) 618 609 Tensile Modulus (g/%strain) 19.83 23.39 Friction 0.167 0.166 Sensory Softness 17.13 17.58

EXAMPLE 13

This example illustrates the effect of rubber roll hardness on thetissue product converted using the differential depth emboss process. Abase sheet similar to that used in example 12 was used here. The basesheets were converted to two-ply tissue using the differential depthemboss process. Instead of using the same hardness (i.e., 40 ShoreDurometer A) of rubber rolls for both nips, a harder rubber roll (i.e.,greater than 40 Shore Durometer A) was used at the light emboss nip (orthe second nip) where the two plies are joined or nested together. Therubber roll hardness ranged from 40 to 80 Shore Durometer A at the lightemboss nip. For one condition, both softer rubber rolls (i.e., 40 ShoreDurometer A) were replaced by harder rubber rolls (i.e., 55 ShoreDurometer A). The emboss pattern shown in FIG. 8 was used in thisexample. Four different penetration depths were run in each condition.The basis weight of the converted two-ply tissue was 18 to 20 lbs/3000square ft. Physical test results are plotted in FIGS. 22-25. FIG. 22shows that the effect of rubber roll hardness on the caliper ofdifferential depth embossing products is not significant. The differencein caliper among differential depth embossing products is within 0.003″per 8 sheets.

The effect of rubber roll hardness on the tensile modulus and frictionare not significant as shown in FIGS. 23 and 24. A similar trend isobserved for the sensory softness result as shown in FIG. 25. Thedifference in softness value among differential depth embossing productsis less than 0.4 units which is significant difference at 95% confidencelevel. Based on results, the harder rubber roll (i.e., greater than 40Shore Durometer A) can replace the softer roll (i.e., 40 Shore DurometerA) at the light emboss nip. The aforementioned result differs from thatdescribed in U.S. Pat. No. 3,708,366. U.S. Pat. No. 3,708,366 statesthat the rubber roll used as the light emboss nip is preferred to besofter than the rubber roll used at the heavy emboss nip. While notwishing to be bound by theory, it is believed that the likelyexplanation for the difference in results between the present inventionand the disclosure in U.S. Pat. No. 3,708,366 is due toelongated/non-elongated and gently rounded emboss patterns used in thepresent invention. These patterns are less likely to form sharpembossments in the ply when using hard rubber rolls.

EXAMPLE 14

This example illustrates the effect of adhesive on tissue productconverted using the differential depth emboss process. Rubber rolls with40 Shore Durometer A were used. The base sheet was similar to that usedin Example 12 and was converted to two-ply tissue using the differentialdepth emboss process. Adhesive was applied on extrusions at the backside of the top ply across the web. The adhesive was applied using anapparatus similar to that shown in FIG. 3A. The emboss patternillustrated in FIG. 8 was used in this example and four differentpenetration depths were run for each condition. FIGS. 26 and 27 showthat the effects of adhesive on the caliper and the tensile modulus ofthe differential depth embossing tissue product are not significant.FIG. 28 shows that the differential depth embossing product withoutadhesive applied has a lower friction than the differential depthembossing product with adhesive applied. The differential depthembossing product without adhesive applied has better softness as shownin FIG. 29. The difference in softness value is more than 0.4 unitswhich is a significant difference at 95% confidence level. Compared tothe product with adhesive applied, the product without adhesive appliedhas lower friction and better softness. The aforementioned results areconsistent with those found in Examples 6 and 7. Thus, applying adhesiveis not preferred for running the differential depth embossing process.

EXAMPLE 15

This example illustrates the effect of adhesive on a tissue productconverted using the differential depth emboss process. The onlydifference between Example 14 and Example 15 is the emboss pattern. Inthis example, an emboss pattern like that shown in FIG. 6A was used.Four different penetration depths were run for each condition. FIG. 30shows that the adhesive did provide a little advantage for generatingbulk. FIG. 31 shows that both differential depth embossing products withand without adhesive applied have a similar tensile modulus at equal GMtensile strength. As the penetration depth increases, the differentialdepth embossing product without adhesive applied has lower friction asshown in FIG. 32. FIG. 33 shows that the differential depth embossingproduct without adhesive applied has better softness. The difference insoftness value is more than 0.4 units which is significant difference at95% confidence level. The sensory softness result is consistent withthat found in Example 14. Thus, by applying adhesive for running thedifferential depth embossing process, the tissue softness may bereduced.

EXAMPLE 16

This example presents a comparison between tissue product convertedusing the differential depth emboss process and that converted using theconventional emboss process. Rubber rolls with 40 Shore Durometer A wereused for both processes. The base sheet was similar to that used inExample 12. Four penetration depths were run for each process and theemboss pattern used for each emboss process was similar to that shown inFIG. 6A. The basis weight of the two-ply tissue product was 18 to 20lbs/3000 square ft. The conventional product has a higher caliper thanthe differential depth embossing product at equal GM tensile strength asshown in FIG. 34 FIG. 35 shows that the differential depth embossingproduct has a higher tensile modulus at equal GM tensile strengthbecause of the light emboss at the second nip. FIG. 36 shows that thedifferential depth embossing product has lower friction at equal GMtensile strength. Compared to the conventional product, the differentialdepth embossing product has better softness as shown in FIG. 37.

EXAMPLE 17

This example presents a comparison between the differential depth embossproduct and the conventional tissue product. The only difference betweenExample 16 and 17 is the emboss pattern. The emboss pattern shown inFIG. 8 was used in this example. The differential depth embossingproduct has higher caliper at equal GM tensile strength as shown in FIG.38. The test results of tensile modulus, friction and sensory softnessare plotted in FIGS. 39-41. Compared to Example 16, the results areconsistent with the differential depth embossing product having lowerfriction, higher tensile modulus, and better softness. Althoughdifferent emboss pattern were used in Examples 16 and 17, thedifferential depth emboss product always has better softness than theconventional product.

EXAMPLE 18

This example compares the differential depth emboss product and theconventional tissue product. Both products were converted on thecommercial machine. Tissue base sheets were made from a furnishcontaining 30% Southern hardwood kraft, 20% Northern softwood kraft and50% recycled fibers. Two-ply tissue was converted using the conventionalemboss process at a penetration depth 0.047 inches. For the differentialdepth embossing product, the penetration depth was 0.075 inches for thetop ply and then the top and bottom plies were embossed together at apenetration depth of 0.035 inches. The rubber roll hardness used in bothprocesses is 40 Shore Durometer A. Both processes used the same embosspattern illustrated in FIG. 8. Table 11 below lists the physicalproperties and sensory softness result. The differential depth embossingproduct has higher caliper, lower friction, higher tensile modulus andbetter softness. The difference in softness value is greater than 0.4units which is significant difference at 95% confidence level. Theresults for commercially made products are consistent with thoseobserved for pilot products used in Examples 3, 4 and 5.

TABLE 11 Physical Properties of Two-Ply Tissue Products DifferentialDepth Conventional Emboss Product Emboss Product (40/40 Sha) Pene. Depth(×0.001″) 47 75/35 Basis Weight (lbs/ream) 18.7 18.8 Caliper(0.001″/8st) 72.6 73.3 MD Dry Tensile (g/3″) 1065 1056 CD Dry Tensile(g/3″) 417 405 GM Dry Tensile (g/3″) 666 654 Tensile Modulus (g/%strain) 19.0 21.1 Friction 0.154 0.151 Roll Diameter (inch) 4.2 4.19Roll Compressibility (%) 19.0 21.1 Sensory Softness 17.16 17.72

EXAMPLE 19

This example illustrates a comparison between the differential depthemboss product and the conventional tissue product. The differencesbetween Example 18 and Example 19 involve the base sheet and thepenetration depth. The basis weight of the tissue base sheet ranges from11-13 lbs/3000 square feet. Base sheets were made from a furnishcontaining 60% Northern hardwood kraft and 40% Northern softwood kraft.Two-ply tissue was converted using the conventional emboss process at apenetration depth of 0.057 inches. For the differential depth embossingtissue product, the penetration depth was 0.088 inches for the top ply,and then the top and bottom plies were embossed together at apenetration depth of 0.038 inches. Table 12 below lists the physicalproperties and sensory softness result. The differential depth embossingproduct has a higher caliper, lower friction, and better softness. Thedifference in softness value is greater than 0.4 units which issignificant difference at 95% confidence level. Both tissue productshave similar tensile modulus value. The sensory softness result is thusconsistent with those found in Example 10.

TABLE 12 Physical Properties of Two-Ply Tissue Products DifferentialDepth Conventional Emboss Product Emboss Product (40/80 Sha) Pene. Depth(×0.001″) 57 88/38 Basis Weight (lbs/ream) 26.6 26.6 Caliper(0.001″/8st) 102.9 106.1 MD Dry Tensile (g/3″) 896 868 CD Dry Tensile(g/3″) 346 332 GM Dry Tensile (g/3″) 557 537 Tensile Modulus (g/%strain) 13.2 13.4 Friction 0.159 0.156 Roll Diameter (inch) 4.15 4.18Roll Compressibility (%) 22.2 21.1 Sensory Softness 19.15 19.91

EXAMPLE 20

This example illustrates the effect of steam preconditioning on two-plytissue converted using the differential depth emboss process. Basesheets were made from a furnish containing 35% Northern hardwood kraftand 65% Northern softwood kraft. The emboss pattern shown in FIG. 8 wasused in this example. The base sheets were converted using thedifferential emboss process with steam preconditioning at both nips asshown in FIG. 5. The set-up was substantially the same as that shown inFIG. 5. Three penetration depths were run for each condition. Comparedto the differential depth embossing product without steampreconditioning, the differential depth embossing product with steampreconditioning has a much higher caliper and lower tensile modulus atequal GM tensile strength as shown in FIGS. 42 and 43. FIG. 44 showsthat the effect of friction on both products are not obvious. Thefriction for the differential depth embossing product with steampreconditioning is quite variable as shown in FIG. 44. Running thedifferential depth emboss process with steam preconditioning can providetwo-ply tissue with more bulk and lower modulus which can improve tissuesoftness.

EXAMPLE 21

This example provides a comparison between the differential depthembossing product and the conventional product converted using theemboss pattern described in U.S. Pat. 3,708,366. A base sheet similar tothat used in Example 17 was converted to 2-ply tissue using thedifferential depth emboss process and the conventional emboss process.Each process was run at four penetration depths. The effect of adhesiveon the differential depth embossing product was also studied. Thesensory softness test result is plotted in FIG. 45. The difference insoftness value between the differential depth embossing product and theconventional product is less than 0.4 units which is significantdifference at 95% confidence level. In the previous examples, thedifferential depth embossing product always possessed better softnessand 0.4 units or more higher than the conventional product. Thedifferential depth embossing product with adhesive applied has lowersoftness value than the differential depth embossing product withoutadhesive applied. The aforementioned result is consistent with theresults observed in Example 13. Applying adhesive when running thedifferential depth emboss process decreases tissue softness. Thephysical attributes are measured and plotted in FIGS. 46-48. FIG. 46shows no significant difference between the differential depth embossingproduct and the conventional product. In previous examples, thedifferential depth embossing product had lower friction than theconventional product. Thus, as can be seen, improving tissue softnessrequires not only the differential depth emboss process but also aspecific emboss pattern as described above.

Table 13 below sets forth a comparison of the aspect ratio of the threeemboss patterns shown in FIGS. 6A, 7 and 8 as well as the emboss patterndescribed in U.S. Pat. No. 3,708,366. The table also sets forth acomparison of the sensory softness for tissue embossed usingdifferential depth embossing as well as the conventional process foreach of the emboss patterns.

TABLE 13 Comparison between The Current Invention and The Prior ArtAspect Ratio Sensory Sensory (Length/ Radius Softness Softness EmbossPattern Width) (×0.001″) (DDE) (Conv.) FIG. 8 emboss 4.01 10 17.6 17.2design FIG. 7 emboss 5.08 10 18.1 17.0 design FIG. 6A emboss 6.58 1017.8 17.1 design Prior art emboss 1.0 5 16.9 16.7 design embodied inU.S. Pat. No. 3,708,366

It is apparent from the foregoing that utilizing the differential depthembossing technique with a known emboss pattern such as that describedin U.S. Pat. No. 3,708,366 does not improve sensory softness. It is onlywhen the differential depth embossing technique is combined with theunique emboss patterns having the characteristics described above andillustrated by way of example in the drawing figures that an improvementin sensory softness is achieved.

The embodiment of the present invention described above involvestreatment of the paper product utilizing an embossing technique.However, a different type of paper treatment can also be utilized toapply a marking to the paper having the characteristics shown in FIGS.6A, 7 and 8. For example, a debossing paper treatment can be employed toproduce a multi-ply paper product as shown in FIG. 50. The multi-plypaper product 100 includes at least two plies 102, 104. The two plies102, 104 are bonded or connected together by the pattern 106 that isimpressed upon the multi-ply paper product. The pattern 106 that isimpressed upon the multi-plies 102, 104 advantageously has the shape andcharacteristics of any one of the emboss patterns described above andillustrated in FIGS. 6A, 7 and 8. The impressed pattern is applied tothe paper product so one surface 105 of the paper product is essentiallyflat and the other is impressed with the pattern 106.

The multi-ply paper product 100 shown in FIG. 50 can be produced usingan apparatus similar to that shown in FIG. 49. The apparatus includes anunwind roll 110 on which is wound a multi-ply paper product such astissue 112. As the sheet passes from the unwind roll 110 to a firstreceiving roll 114, the multi-ply paper product 112 can be brought intocontact with water. The water can be applied to the sheet 112 in theform of steam by passing the sheet 112 over a tank 116 containing waterthat is heated to a temperature greater than or equal to the boilingpoint of water. Steam is thus released from the tank and comes intocontact with the surface of the sheet 112. The amount of steam appliedcan vary, although it is preferably less than approximately 3% by weightof the sheet 112, more preferably less than 2% by weight. The smallamount of water in the form of steam that is applied to the sheetconstitutes a preparatory step for the next step in the formation of theimpressed pattern on the multi-ply sheet that is designed toconsiderably improve the quality of the impressed pattern. In thisregard, the steam has an advantageous affect on the definition anduniformity of the pressed pattern. Of course, liquid can be applied tothe sheet 112 in forms other than steam, such as, for example, byspraying fine droplets.

The sheet 112 is conveyed to the first receiving roll 114, and is thenpassed between the first receiving roll 114 and a steel engraved roll118. The steel engraved roll 118 is a hard and non-deformable roll. Thefirst receiving roll 114 is substantially elastic. The sheet 112 thenmakes a second pass between the engraved roll 118 and a second receivingroll 120. The second receiving roll 120 is preferably substantiallyelastic.

The engraved roll 118 can be heated, preferably to a temperature lyingwithin the range of approximately 50° C.-100° C., or preferablyapproximately 75° C. It has been found that the combination of theapplication of water in the form of steam and the use of a heatedengraved roll provides an advantageous impressed pattern upon themulti-ply sheet 100 shown in FIG. 50.

The first and second receiving rolls 114, 120 possess a high hardness,greater than Shore-D 80 and preferably greater than Shore-D 90.

FIG. 51 illustrates a slightly different two-ply paper product in whicha pattern is impressed upon the two-ply paper product in a slightlydifferent manner from that described above. Once again, the impressionor marking that is applied to the paper product advantageously possessesthe shape and characteristics of any one of the embossed patternsdescribed above and illustrated in FIGS. 6A, 7 and 8.

As seen in FIG. 51, the paper product includes two plies 120, 122. Thesheet is provided with a series of impressed regions 124 having theshape and characteristics of any one of the embossed patterns describedabove and illustrated in FIGS. 6A, 7 and 8. The sheet is produced bypassing the two-ply paper product through a nip formed between anengraved roll and a back up roll. As the two plies 120, 122 pass intothe nip, portions of the two-ply paper product corresponding to theprojections on the engraved roll are impressed. This compression causesthe cellulosic fibers in the two plies 120, 122 to become intermingledand connected with one another.

Another aspect of the present invention illustrated in FIGS. 52 and 53relates to a different process for producing for producing a two-plytissue. This method involves the production of a tissue having a heavilyembossed pattern, but which is not perceived as being rough to theconsumer. Referring to FIG. 52, a rubber roll 200 is positioned inabutting relation to a steel engraving roll 202. An adhesive applyingdevice 204 is positioned adjacent the steel engraving roll 202. Theadhesive applying device 204 includes an adhesive supply 206 and arotatable application roller 208.

A base sheet or substrate 210 is conveyed around the rubber roll 200 andthen enters a nip 212 between the rubber roll 200 and the steel engravedroll 202. The rubber roll 200 presses the base sheet 210 into thepattern formed on the engraved steel roll 202 to produce the desiredembossing pattern. The rubber roll 200 can be a relatively soft rubberhaving a low durometer to thereby impart a heavy boss to the base sheet210. As the base sheet 210 is conveyed around the outer surface of thesteel engraved roll 202, the backside of the embossed base sheet 210passes by the adhesive application roller 208 which applies adhesiveonly to the protuberances or nips on the back of the heavily embossedsheet.

As the embossed base sheet 210 is being conveyed, an essentially orsubstantially flat backing sheet 214 is conveyed past a roller 216 andthen into engagement with the back surface of the embossed base sheet210. As a result, the backing sheet 214 is adhered to the embossed basesheet 210. A marrying roll 218 is preferably provided adjacent the outersurface of the steel engraved roll 202 to facilitate adherence betweenthe two sheets 210, 214. Because the adhesive is only applied to thenips or projections on the embossed sheet 210, the flat backing sheet214 is adhered to the embossed base sheet 210 only at those places. Thisselective positioning of the adhesive is advantageous from thestandpoint of not excessively interfering or hindering the perceivedsoftness of the resulting sheet. At the same time, the perceivedstrength of the sheet is increased significantly.

It is also possible with this method to improve the perceived quiltedappearance of the resulting product by making it appear puffier. Thiscan be achieved by utilizing mismatch in the stretch between the twosheets 210, 214. This mismatch in the stretch of the two sheets can beachieved or controlled by controlling the relative feed rates of the twosheets, so that one sheet is fed at a faster rate than the other.

In the resulting product, the protuberances or nubs on the backside ofthe heavily embossed sheet 210 are masked or covered by thesubstantially flat un-embossed backing sheet. The perceived softness ofthe resulting two-ply tissue is thus improved. This method also makes itpossible to easily color decorate the resulting tissue product by usingcolored adhesive to join the sheets.

A further advantage associated with this method is illustrated in FIG.53. In this variation, dual depth embossing is employed. With dual depthembossing, some of the embossments 220 are deeper than other embossments222. This could be easily achieved by appropriately configuring theouter surface of the steel engraved roll 202. In addition to differentdepth embossing, the different depth embossments 220, 222 can be of adifferent configuration to impart an attractive appearance to thefinished tissue product. For example, the deeper embossments 220 can bein the form of tulip-shaped embossments while the shallower embossments222 can be dot-shaped embossments.

A further refinement provided by the variation shown in FIG. 53 is thatadhesive can be applied even more selectively to only portions of thebacking side of the embossed sheet 210′. That is, through use of anadhesive application device such as that shown in FIG. 52, adhesive isapplied to only the longest protuberances or nubs forming a part of theembossed pattern. Thus, adhesive is only applied in very small selectedareas between the two sheet 210′, 214 so as not to significantlyinterfere with the perceived softness of the resulting sheet, while atthe same time allowing realization of an increase in the perceivedstrength of the resulting sheet.

Another aspect of the present invention illustrated in FIGS. 54 and 55relates to a different process for producing a single ply tissue havinga one-sided finished product appearance. In accordance with this aspectof the present invention, double nip embossing is carried out throughuse of one steel roll and two rubber rolls possessing differentdurometer or hardness characteristics. As illustrated in FIG. 54, thearrangement for producing double nip embossing on the same steelengraved roll includes a first rubber roll 300, a second rubber roll 302and a steel engraved roll 304 located between the first and secondrubber rolls 300, 302. The first rubber roll 300 and the second rubberroll 302 possess different hardness or durometer characteristics. Thefirst rubber roll 300 is made of a rubber material possessing relativelymedium durometer characteristics while the second rubber roll 302 ismade of a rubber possessing relatively soft durometer characteristics.Both the first and second rubber rolls 300, 302 engage the steelengraved roll 304 and press against the steel engraved roll. The steelengraved roll 304 is preferably engraved so that between 5% and 50% ofits exterior surface constitutes an indented pattern while the remainingportion is not indented.

As further illustrated in FIG. 54, a single base sheet or substrate 306is conveyed around the exterior surface of the first rubber roll 300 andis then conveyed into the nip 308 between the first rubber roll 300 andthe steel engraved roll 304. As the substrate 306 is conveyed into thenip 308, the first rubber roll 300 starts forming the base sheet orsubstrate 306 around the protruding elements of the steel engraved roll304 or presses the base sheet 306 into the indented portions of thesteel engraved roll 304.

The base sheet 306 continues to be conveyed along the rotating exteriorsurface of the steel engraved roll 304 and then enters a second nip 310formed between the second rubber roll 302 and the steel engraved roll304. Because the second rubber roll 302 is made of a softer rubbermaterial having a lower durometer, the rubber will flow more deeply intothe steel engraved roll 304. The embossed sheet exiting the second nip310 will possess a one-sided appearance.

The use of this arrangement involving two rubber-to-steel nips improvesthe softness perception of the resulting tissue product, imparts morebulk to the resulting tissue product, contributes to providing a tissueproduct having a better appearance, and creates a truer lookingone-sided tissue product.

A variation on the arrangement shown in FIG. 54 is illustrated in FIG.55 and involves the use of the first rubber roll 300, the second rubberroll 302, and the steel engraved roll 304. In addition, a third rubberroll 320 is employed and is positioned adjacent the first rubber roll300. Thus, the same effects and advantages discussed above in connectionwith the arrangement shown in FIG. 54 are achieved. In addition, theinclusion of the third rubber roll 320 provides a rubber-to-rubberstation that imparts additional calendering and softness treatment tothe base sheet 306.

It is thus possible in accordance with this aspect of the presentinvention to produce a one ply embossed tissue having a one-sidedfinished product appearance. The first rubber roll is designed to embossin a way that begins to set the desired pattern while the softer secondrubber roll causes the sheet to flow deeper into the indented pattern onthe engraved roll, thus developing the one-sidedness required anddesired for a premium single ply product.

The principles, preferred embodiments and modes of operation of thepresent invention have been described in the foregoing specification.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments described. Further,the embodiments described herein are to be regarded as illustrativerather than restrictive. Variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent invention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the invention be embraced thereby.

1. A method of producing a single-ply embossed tissue comprising:conveying a base sheet through a nip between a first impression rollmade of rubber and a pattern roll to push portions of the base sheetinto indented portions of the pattern roll; conveying the base sheetthrough a nip between the pattern roll and a second impression roll madeof rubber having a lower hardness than the rubber from which the firstimpression roll is made to push the portions of the base sheet furtherinto the indented portions of the pattern roll to produce a single-plyembossed tissue.
 2. The method according to claim 1, including conveyingthe base sheet between the first impression roll and another impressionroll prior to conveying the base sheet through the nip between the firstimpression roll and the pattern roll.
 3. The method according to claim1, wherein from 5% to 50% of the pattern roll is indented and theremainder of the pattern roll is not indented.
 4. The method accordingto claim 1, wherein the first impression roll is made of a rubbermaterial possessing relatively medium durometer characteristics and thesecond impression roll is made of rubber possessing relatively softdurometer characteristics.
 5. The method according to claim 2, whereinthe third impression roll is made of rubber.